Anti-lock brake systems are finding acceptance in the automotive marketplace resulting in an increasing number of vehicles being equipped with such braking systems. The anti-lock brake systems monitor the rotational speed of two or more of the vehicle's wheels and a microprocessor detects when one or more of the wheels is approaching a locked state. The microprocessor will, in response to detecting one or more wheels approaching a locked state, reduce the braking torque being applied to the associated wheel, preventing it from locking up. These systems are designed to maintain a maximum coefficient of friction or a minimum slip condition between the wheel and the road surface. Although they work well, these systems are relatively complex and expensive.
Schiel et al, in U.S. Pat. No. 4,966,420, discloses a simplified best effort anti-lock brake system. In this system, the input to the vacuum brake booster is controlled by an ABS electronic control to reduce the braking torque to all four wheels when at least one of the wheels is detected as approaching a lock-up state. One problem with this type of anti-lock brake control is that the brake pedal pulsates when the anti-locking brake system is activated. This pulsation of the brake pedal has been found to be disturbing to many of the vehicle operators since it gives them a sense of insecurity.
The invention is a single channel best effort anti-lock brake system which eliminates the pulsation of the brake pedal, and is significantly less complex than the anti-lock brake systems currently available for automotive vehicles.